The present invention relates to a power assist system for operating a vehicle clutch mechanism through an operation cable, and is particularly concerned with a power assist system for a vehicle clutch mechanism capable of relieving the operating force of a clutch lever in a motorcycle or clutch pedal in an automobile.
A motorcycle and an automobile are each provided with a clutch mechanism for intermitting a driving force of an engine on a driving system which includes a transmission mechanism, at the time of starting and speed changing operations. The clutch mechanism is subjected to a clutching operation by having a clutch operating force transferred through an operation cable by manual operation of a clutch lever or footing operation of a clutch pedal. In such a case, a leverage is applied to the clutch lever or the clutch pedal and an operating force is moderated by increasing the leverage.
Moreover, the motorcycle and the automobile have a hydraulic power clutch for effecting a moderated intermittent operation of the clutch mechanism. With the hydraulic power clutch, an intermittent operation of the clutch mechanism is carried out by utilizing a negative pressure, such as suction or the like, of an oil pump or an oil pressure generated on the oil pump so that the operating force of the clutch lever or the clutch pedal is moderated.
Conventional hydraulic power clutches are not applicable to a clutch mechanism employing an operation cable to which a clutch operating force is transferred through the operation cable. Moreover, to provide the hydraulic power clutch as mentioned, a multiplicity of associated parts must be refabricated and much time and labor are hence required, which may lead to an increase in cost.
Further, in the case of a clutch mechanism employing an operation cable, the operating force of the clutch lever or the clutch pedal is moderated by increasing the leverage. However, the clutch operating force cannot be decreased sharply. Particularly, in a motorcycle, a speed change operation must be performed often when travelling on a mountain path with many byways or jamming, and hence, the clutch lever must be manipulated in each case. However, when the clutch lever is manipulated frequently, the clutch operating force cannot be moderated sufficiently only by the leverage. Therefore, operating conditions are made worse and the manual operation unduly burdened, thus resulting in an uncomfortable driving condition.